As one example of an odor source, wastewater lift stations or pump stations are used to “lift” liquid uphill—against gravity. They are an essential component of a wastewater collection system which takes wastewater from residents and businesses in a community and pumps it to a sewage treatment plant.
Managing a network of wastewater lift stations that pumps to the treatment plant is challenging. Accidental discharge of sewerage is a serious environmental hazard. Pumps can block, level sensing devices can fail, pipes can crack, lightning or power surges can damage control equipment, and power to control pumps can be interrupted. Discharge of gasses is also problematic. Not only are the discharged gasses pollutants, but some are quite odiferous. Thus, nearby residents and businesses may encounter extremely unpleasant odors originating from a lift station in the vicinity. Foul odors escaping the wet well air space has been a continual problem over the years, particularly in residential neighborhoods.
Odors are inevitable. Wastewater undergoing storage, transportation, and treatment will produce odors. The production of odors comes as a result of wastewater composition and depends on the environment and the time that the particular environmental conditions have existed. During some conditions, odors will escape through vents.
Gaseous emissions may include hydrogen sulfide (H2S), ammonia (NH3), carbon dioxide (CO2), and methane (CH4). Some other gasses resulting from biological activity are nitrogen (N2), oxygen (O2), and hydrogen (H2). Most common sewer gasses are odorless except for hydrogen sulfide, which has the strong odor of rotten eggs, and ammonia, which has the odor of concentrated urine. The principal odor-causing gas in a wastewater lift station is hydrogen sulfide.
Many methods have been used over the years to control or mask the foul odors including: 1) feed of chemicals such as hydrogen peroxide into the liquid; 2) aeration of the liquid; 3) chemical scrubbers; 4) biological scrubbers; 5) oxidation in the wet well air space; and 6) activated carbon absorption. Chemicals can be extremely expensive. Several of the methods are not energy efficient or cost effective. Maintenance can also be expensive and cause excessive downtime of equipment. A cost effective odor reduction system that does not require replenishment of chemicals or a substantial capital investment is needed.
Further complicating matters, the volume and rate of odiferous gasses emitted can vary considerably based upon various factors, including temperature, dissolved oxygen, pH and well conditions such as volume. Hydrogen sulfide production increases at higher wastewater temperatures, and hydrogen sulfide released from wastewater will combine with water vapor to form sulfuric acid, which attacks sewers, manholes, wet wells, and other facilities. The presence of certain types of gasses in sewers depends on oxygen availability. When little oxygen is present, biological degradation is through anaerobic processes and the predominant gasses released will be hydrogen sulfide and methane. Another condition that promotes the release of hydrogen sulfide gas is wastewater pH. Sulfide exists in wastewater in the ionic form above pH 7.5. Below pH 7.5, sulfide leaves the wastewater in the gaseous form. Yet another condition is the volume of wastewater in a well and vapor pressure. When the wastewater level falls due to pumps pumping the liquid from the wet well, foul odor gasses are not discharged and fresh air is sucked into the wet well. However, when wastewater level rises due to increased wastewater production or precipitation, odiferous gasses are expelled. Thus, an effective odor reducing system must adapt to such changing conditions.
The invention is directed to overcoming one or more of the problems and solving one or more of the needs as set forth above.